It is well known to provide prosthetic joint components for replacing damaged and deteriorating joints. Typical joint replacements require resection of distal or proximal end of one or more of the bones forming the joint to be replaced to permit the prosthetic device to be firmly attached to the bone without altering the length of the limb in which the joint is being replaced. Joint component manufactures have recognized the benefits to be derived from joint replacement procedures that require less invasive surgeries with smaller incisions and more kinematically correct implants. Additionally, as younger patients are receiving joint replacements, there is a desire to provide joint replacements that allow the patient to recover from the replacement surgery more quickly, provide better function and are more durable.
One key to a kinematically correct durable implant is the interface between the bone and the implant. Due to the likelihood of eventual failure of a prosthesis there is always the possibility of the need for a replacement prosthetic procedures that will require further bone resections. Thus, it is preferable to resect a sufficient area of the bone to permit proper seating of the implant on the bone and to facilitate in-growth and/or on-growth of the bone to the implant, while reducing the amount of bone resected to allow further bone resections to accommodate revision or replacement of the implant. One method utilized to address the competing concerns of providing adequate bone resection to properly seat an implant and reducing the amount of bone resected to facilitate revision or replacement of the implant is to provide a surface replacement implant. Surface replacement implants require shaping the bone into curved or multiple non-coplanar surfaces rather than flat surfaces. It would be preferable to provide instruments for resecting the articulating surfaces of a bone to receive an implant that are minimally sized and that accurately guide a cutting tool to create curved surfaces for receipt of a surface replacement implant.
One type of surface implant in common use is the uni-compartmental knee system. The tibia (leg bone) and femur (thigh bone) meet at the knee and divide into medial (inner) and lateral (outer) tibio-femoral compartments. The patella (kneecap) in the front of the knee articulates with the trochlea (kneecap socket) of the femur to form the patello-femoral compartment. The tibio-femoral compartments are used for walking. The patello-femoral compartment is used for kneeling, squatting and stair-climbing. In unicompartmental knee arthroplasty, one of the knee's tibio-femoral compartments, usually the medial one, is resurfaced. This should be contrasted to total knee arthroplasty (TKA), which resurfaces both of the tibio-femoral compartments and usually the patello-femoral compartment. With the increased prevalence of unicompartmental knee arthroplasty (UKA), a prosthetic system which provides a conservative approach in terms of both instrumentation and implant design is important.
Age and activity level factor into all reconstructive procedures. Typically, the state of arthritis determines the treatment. With the advancement of minimally invasive techniques that support uni-compartmental knee reconstruction, a growing number of patients are offered this alternative for relief from the disabling pain of arthritis and for the potential benefits of a rapid recovery. Some patients have very significant arthritis changes in only one part of their knee, frequently on their inner or medial side. If there are no other major arthritis changes on the other side of the knee or under the knee cap, partial knee replacement (officially “uni-compartmental knee replacement”) is indicated. Uni-compartmental knee replacement is a less invasive partial knee replacement procedure.
Benefits of uni-compartmental knee arthroplasty over total knee arthroplasty include 1) faster recovery, 2) less pain, 3) greater range of motion, 4) greater feeling of normalcy, 5) better alternatives when the prosthesis wears out, 6) no blood transfusions and 7) no need for blood thinners. Many of these benefits arise because with a uni-compartmental arthroplasty the surgery is less extensive, the incision is smaller, and there is less tissue trauma than in a TKA. A primary TKA will usually last 10-15 years. When it fails it must be replaced with a Revision TKA (RTKA). RTKAs have a high complication rate and don't last as long as primary TKAs. The uni-compartmental arthroplasty buys time. When it wears out it is replaced by a TKA. Patients may never need an RTKA or if they do, they generally will have gotten many more years use out of their TKA. By utilizing a uni-compartmental arthroplasty instead of a TKA, patients of any age can benefit. Older patients benefit from the reduced severity of the procedure and easier recovery. Younger patients benefit because when the prosthesis eventually fails (all prostheses fail faster in younger patients), they will be able to have it replaced with the better primary TKA as opposed to the less desirable RTKA.
Some prior art uni-compartmental knee systems have provided either limited instrumentation, making reproducible alignment difficult, or bulky instrumentation which requires more intrusive surgery. A few prior art uni-compartmental knee systems are designed with bone conserving femoral and tibial components that provide reproducible results utilizing a minimal incision. The resurfacing femoral implant conserves more quality bone stock compared to contemporary full resection femoral implants.
One such uni-compartmental knee system is the PRESERVATION™ Uni-compartmental Knee, available from DePuy Orthopaedics. The PRESERVATION™ Uni-compartmental Knee offers the surgeon fixed and mobile bearing tibial options specific to patient requirements. The system supports a less invasive procedure with instruments that provide for joint line restoration, load sharing balance, and component alignment. The PRESERVATION™ uni-compartmental knee system utilizes a technique that minimizes bone resections for later total knee arthroplasty options. The system is adapted to be utilized with Computer Aided Surgical (“CAS”) technology.
The technical challenges of less invasive uni-compartmental knee surgery are becoming more apparent, even for the specialist arthroplasty surgeon. CAS technology has a clear role to play in less invasive surgery. CAS technology provides enhanced surgical vision which optimizes visualization of the critical anatomical landmarks, irrespective of the length of the incision. CAS technology offers the surgeon a level of vision and control that is difficult to achieve with non-CAS enabled, less invasive, procedures. With the key anatomy fully visualized, finger-tip instrument adjustment allows the surgeon to transfer on-screen planning to the table with greater precision. Virtual planning and kinematic assessment software provided with CAS technology allows implant positioning for each patient prior to any bone cuts being made.
The disclosed invention provides guides and a cutting tools configured to follow the guides to resect a bone to receive a surface replacement implant. The guide includes features to maintain the correct alignment of the cutting tool while providing sufficient freedom to create cuts having the desired depth for receiving a surface replacement prosthesis. The guides and cutting tools are configured to be effectively used in a minimal incision procedure while still offering the surgeon the alignment guides needed for consistent results. The disclosed guides are configured for utilization with CAS technology. Thus, reproducible outcomes are possible within a minimal incision.
According to one aspect of the disclosure, a bone resection tool for resecting an end of a bone along a surface having a curvature comprises a guide, a cutting tool and a track follower. The guide is configured to be removably attached in a fixed position to the end of the bone. The guide is configured to include a track exhibiting a curvature generally corresponding to the curvature of the surface to be resected in the bone. The cutting tool includes a cutting face. The track follower is configured to couple to the cutting tool and cooperate with the track to facilitate reciprocation of the cutting tool relative to the guide to induce the cutting face to resect the bone along the surface having the curvature.
According to another aspect of the disclosure, a method for cutting a bone along a curved surface conforming to the curvature of a curved surface of the underside of a prosthetic component comprises the steps of incising the tissue surrounding the surface of the bone, positioning a guide alongside the surface of a bone to be cut, affixing the guide to the bone, interconnecting a cutter having a cutting face with the guide, maintaining the cutting face generally parallel to the tangent of the curved surface and traversing the cutting face along the bone while guiding the cutter along the track. The tissue incision incises the tissue surrounding the surface of the bone to be cut in a minimally invasive fashion. The positioned guide includes a track configured to assimilate the curvature of the curved surface of the underside of the prosthetic component.
The accompanying drawings, which are incorporated in and constitute part of the specification, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the invention. It is to be understood, of course, that both the drawings and the description are explanatory only and are not restrictive of the invention.
Corresponding reference characters indicate corresponding parts throughout the several views. Like reference characters tend to indicate like parts throughout the several views.